. This study focuses on the use of antifreeze peptides in the development of an improved method for cryopreservation of bone marrow progenitor cells. Recombinant antifreeze peptides have been found to inhibit migratory recrystalization during thawing of erythrocytes and to permit reduction in dimethylsulfoxide concentrations in cryopreservation of the leukemic cell line KG-la. The objective of this proposal is to combine the above observations in the design of a novel bone marrow cryopreservation procedure. Combination of antifreeze peptides with low levels of penetrating and non-penetrating cryoprotectants should remove the problems encountered, due to hemolysis and cell clumping, with classical bone marrow cryopreservation. Success in this project may result in removal of cell processing steps before and after cryopreservation; ultimately resulting in reduced costs, and reduced stem cell losses due to the cytotoxicity, which is associated with bone marrow processing, preservation, and thawing. This study will be performed at the CryoLife Research and Development Laboratories using rabbit bone marrow.